In this application, we propose to investigate treatment using animal models of the genetically heterogeneous blinding disorder, Bardet-Biedl Syndrome (BBS). At least seventeen BBS genes have been reported to date. BBS is a pleiotropic disorder with the primary clinical features of pigmentary retinopathy, obesity, polydactyly, learning disabilities, renal abnormalities and hypogenitalism. BBS patients also have an increased incidence of hypertension, diabetes mellitus and congenital heart defects. The retinal degeneration of BBS is early onset and typically leads to blindness in the second decade of life. The blindness component of the BBS phenotype is the most concerning aspect of the disorder to patients and their families, and hence the component of BBS that we will focus on for treatment. Strategies for treating inherited forms of blindness include gene therapy, stem cell therapy, and pharmacological treatments. Gene therapy can theoretically target the primary gene defective in the specific patient, or alternatively target genes that modify the primary gene. Access to a number of different BBS animal models provides us with the opportunity to examine a variety of different approaches to treat the blindness component of BBS. In the proposed studies, we will utilize zebrafish to identify the specific genetic types of BBS that are most likey to be readily treatable with gene replacement therapy, and based on the zebrafish data, we will select at least six BBS mouse models to be treated with gene therapy (specific aim 1). In specific aim 2, we will pursue the hypothesis that some forms of BBS can be treated by alteration of the expression of modifier genes. Finally, in specific aim 3, we hypothesize that specific molecular pathways modify BBS phenotypes. We will test this hypothesis by using pharmaceuticals to treat BBS mouse models targeting specific cellular pathways including apoptosis; endoplasmic reticulum (ER) stress and the unfolded protein response; chaperones; and PDGFR signaling. Our studies will lead to a better understanding of cilia-related retinopathies; assist in classifying which of a number of treatments will best work, and provide an initial step in going from treatment of animal models to human treatment.